Transmission Line Design Intro

7/25/2019 Transmission Line Design Intro

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TransmissionSystemDesign


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SimplestepsforSagCalculation

1. Measurethehorizontaldistancebetweenthetowerattachment

points

(L).

2. Determinetheweightperunitlengthoftheconductor(w).

3. Findthetensionintheline(T).

4. Substitute

these

values

into

the

equation

T

x

y

=

(wx)(x/2)

where

yistheverticaldistancebetweentheattachmentpointandthe

lowestpointintheparabola,andwx istheweightthatactsata

horizontaldistancex/2fromtheattachmentpoint.

5. Solvetheequationfory.Thisyieldsy=wx/(2T).SubstituteL/2

forxsincethecenterbetweenthetowersisthelowspottoget

y=w/(2T)x(L/2),whichsimplifiestoy=wL/8T.

For

example,

the

sag

for

a

cable

with

a

weight

equal

to

1

kilogrampermetertensionedto10,000kgbetweentowers500

metersapartwouldhaveasagequalto(1)(500)/(8)(10,000)=

250,000/80,000=3.125meters.


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Bundle Conductors

2

4 S SSelfGMD D d D d

dDs

d d

d

d

d

dd

Ds

Ds Ds

Ds Ds

Ds Ds

3 29 3

4 3416 2 1.091

S S

S S

SelfGMD D d d D d

SelfGMD D d d d D d


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Inductance72 10 H/m

( )

a

GMDL In

SelfGMD GMR

Capacitance

2 //

anC F m

In GMD SelfGMD


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Insulators


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PotentialDistributioninStringInsulator


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M th d f I i St i Effi i


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Methods

of

Improving

String

Efficiency

1. By

using

longer

cross

arm2. Bygradinginsulators

3. ByusingGuardring


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Documents

Transmission Line Design Intro